Jarek,
There is no question we want this data. I went through much of it in
Toronto and Kingston and I found it to be very good, consistent and
precise. Time-wise it's somewhat current with 2016 ESRI imagery
(sometimes ahead, sometimes slightly behind) and is well-aligned with
it. It offers 3D features (when several buildings appear overlapped
in the dataset) but you just need to be familiar with `building:part`
tag to sort through it. I haven't looked at other provinces but in
Ontario I really have no complaints about dataset quality whatsoever.
Also I don't get Nate's "wildly unsimplified geometries" comment. IMO
geometries are just perfectly detailed.
On Fri, Jan 18, 2019 at 2:00 PM Jarek Piórkowski <[email protected]
<mailto:[email protected]>> wrote:
Some more thoughts from me.
Building outlines, particularly for single-family subdivisions as
seen
in Canadian suburbs, are extremely labour-intensive to map manually.
My parents' house is now on OSM - accurately. They live in a city
with
about 10,000 buildings, and about 0.5 active mappers. This wouldn't
been completed manually in the next 5 years.
An option to do this automatically with a computer algorithm
detecting
objects from imagery could be suggested, but this has not been very
accurate in OSM in the past, even when there is decent imagery. The
only other feasible data source is government, where they have such
data more or less.
The alternative is of course the opinion that we should not have
building outlines until someone goes through and adds the buildings
manually. In practice what I've seen done in Toronto is that bigger
buildings are mapped on best-effort basis from survey and imagery,
while areas of single-family houses are left blank. This isn't
_wrong_, and maybe some prefer this.
I would also like to note that building outlines will _never_ be
completely verifiably up to date. I can't go into most people's
backyards and verify that there isn't a new addition on their
house. A
building might be legally split into two different properties without
it being evident from the street. Imagery is out of date the day
after
it's taken, and proper offset can be difficult to establish in big
cities where GPS signal is erratic. Pragmatically, I can tell you
from
personal experience that building data in lovingly-mapped Berlin is
also worse than 1 meter accuracy. So again: best effort.
What do we get from having buildings? A sense of land use (arguably
replaceable with larger landuse areas). A way to roughly estimate
population density. A way to gauge built-up density. A data
source for
locating buildings in possible flood zones, or fire risk. Statistics:
as open data, queryable by APIs that are already used, in format
more-or-less common worldwide.
Examples were given of rowhouse- or de-facto rowhouse-buildings where
a part is attached to the wrong building. This does not alter any of
the above examples. It's wrong, but is it substantially more wrong
than a blank subdivision, or one with only a few buildings mapped? Is
it better to have a null, or be off by 5%? The legal truth is in
property records, and we can't measure houses with a ruler, so
OSM can
only be a statistical source. And then there's the question of
verifiability - some of these buildings are connected to their
neighbour building inside. I've really struggled at distinguishing
what exactly is a "building" on Old Toronto avenues even with
street-side survey.
Bluntly, OSM is not perfect in Canada. I have pet peeves I can quote,
and I'm sure many of you do as well. If we import, the question is:
are we making it better?
1. Do we want this data?
2. Is it generally of acceptable quality?
3. Is there a mechanism to spot and reject where data is
particularly bad?
Cheers,
Jarek, who should really get back to updating built-last-year
stuff at Fort York
On Fri, 18 Jan 2019 at 09:31, Kyle Nuttall
<[email protected] <mailto:[email protected]>> wrote:
>
> The pilot project that took place in Ottawa for all these
building imports is what got me hooked into OSM in the first
place. I would make only very minor changes here and there. I
even attempted to draw building footprints but got burnt out
after only doing a single street, which was very discouraging for
me to continue.
>
> When I saw the entire neighbourhood get flooded with new
buildings that weren't there before, I was entirely intrigued and
actually got on board with the locals to help with the process.
I've been hooked since and have been to many meetups afterwards.
Helping out with projects completely unrelated to the initial
building import.
>
> I'm entirely of the belief that it is much more encouraging for
a new user to make a minor change (eg. changing `building=yes` to
`building=detached`) than it is to add every single minor detail
to each object from scratch (visiting the location, drawing the
building footprints manually, adding address data, etc.). It's
just overwhelming for a new user.
>
> It is very much a cat-and-mouse type scenario with community
driven projects like OSM. Apparently the issue with this import
is the lack of community involvement but I can for sure tell you
that this import will help flourish the community in the local
areas. Especially if they only need to add or change minor tags
than if they would have had to create all of this data by hand.
With an import this size there is bound to be some errors that
slip through. That's where the community comes through to correct
these minor things.
>
> This is the whole point of OSM. A user creates an object with
as much information as they know and the next user comes and adds
onto that, and the next user adds and/or updates even more.
Neither of those users on their own could have added as much
detail as all of their knowledge combined.
>
> Are we supposed to just wait for a user who can add every
single building with centimetre precision and every bit of detail
simply because we can't? No, of course not. We do the best we can
and have other users who know more than we do build on that.
>
> I fully endorse this import because I would love to see what it
does for the local communities that apparently need to figure
this import out for themselves.
>
> Cheers,
> Kyle
>
> On Jan. 18, 2019 05:40, James <[email protected]
<mailto:[email protected]>> wrote:
>
> As Frederik Ramm once said(sorry i'm paraphrasing from memory
please don't shoot me) There has never been a GO-Nogo for
imports, you bring it up on the mailing lists with reasonable
delay, is there no objections(in this case no one was saying
anything about it for 2-3 weeks) then email the list that the
import would start.
>
> On Fri., Jan. 18, 2019, 12:59 a.m. Alan Richards
<[email protected] <mailto:[email protected]> wrote:
>
> Along the lines of what Jarek said, sometimes silence just
means tacit acceptance, or that it's not that controversial.
There's quite a bit of government data here that is supposedly
"open" but unavailable for OSM, so I'm very glad Stats Can was
able to find a way to collect municipal data and publish it under
one national license. I was surprised myself it hadn't got more
attention, but I'm firmly onboard with more imports if done with
care.
> Manually adding buildings - especially residential
neighborhoods, is about the most boring task I can think of, yet
it does add a lot to the map.
>
> I'll admit I hadn't looked at the data quality myself, but I
just did review several task squares around BC and they look
pretty good. Houses were all in the right place, accurate, and
generally as much or even more detailed than I typically see.
Issues seemed to be mostly the larger commercial buildings being
overly large or missing detail, but in general these are the
buildings most likely to be already mapped. To a large degree,
it's up the individual importer to do some quality control,
review against existing object, satellite, etc. If we have
specific issues we can and should address them, but if the data
is largely good then I see no need to abort or revert.
>
> alarobric
>
> On Thu, Jan 17, 2019 at 7:41 PM Jarek Piórkowski
<[email protected] <mailto:[email protected]>> wrote:
>
> On Thu, 17 Jan 2019 at 21:46, OSM Volunteer stevea
> <[email protected] <mailto:[email protected]>>
wrote:
> > Thanks, Jarek. Considering I am a proponent of "perfection
must not be the enemy of good" (regarding OSM data entry), I
think data which are "darn good, though not perfect" DO deserve
to enter into OSM. Sometimes "darn good" might be 85%, 95%
"good," as then we'll get it to 99% and then 100% over time. But
if the focus on "how" isn't sharp enough to get it to 85% (or so)
during initial entry, go back and start over to get that number
up. 85% sounds arbitrary, I know, but think of it as "a solid B"
which might be "passes the class for now" without failing. And
it's good we develop a "meanwhile strategy" to take it to 99% and
then 100% in the (near- or at most mid-term) future. This isn't
outrageously difficult, though it does take patience and
coordination. Open communication is a prerequisite.
>
> Thank you for this commitment. I wish others shared it.
Unfortunately
> the reality I've been seeing in OSM is that edits which are
90+% good
> (like this import) are challenged, while edits which are 50+% bad
> (maps.me <http://maps.me> submissions, wheelmap/rosemary v0.4.4
going to completely
> wrong locations for _years_) go unchallenged or are laboriously
> manually fixed afterward.
>
> --Jarek
>
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Yaro Shkvorets
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